Frost Dates for 47001 — Aurora, Indiana

Half of springs at Milan 5 NE, IN see their last 32°F night by April 30; only one in ten is past it by April 14, and one in ten still has one after May 15. Planting tender crops after May 5 leaves a 30% risk of a frost on them, after May 9 20%, and after May 15 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 70% of the 125 Indiana stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 16 in half of years, as early as October 3 one year in ten, and holds off past October 29 one year in ten. A hard freeze of 28°F follows 10 days later, around October 26; in spring the one-in-ten date for 28°F is May 4, 11 days before the 32°F one. The freeze-free season lasts 168 days in a typical year, shorter than at 94% of the 125 Indiana stations; it reaches 188 days one year in ten and falls short of 148 one year in ten. On average 128 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 8 days longer, to about May 8, and return around October 6. Severe cold of 16°F or below comes every winter, usually between December 1 and March 13.

July is the warmest month at Milan 5 NE, IN, averaging 83°F by day and 62°F at night; January is the coldest at 37°F and 19°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 44% of years.

Warmth for growing adds up to 3,075 growing degree days a year (base 50°F), fewer than at 78% of the 125 Indiana stations. 35% of them (1,083) have built up by the end of June, and July adds the most, 690.

The nearest other station, Cincinnati-Fernbank, OH, 13 miles east of Aurora and 475 feet lower, has a last frost 17 days earlier (April 13), a first frost 15 days later (October 31), a season 29 days longer.

The first measurable snow (0.1 inch or more) in Aurora usually arrives around December 21, and the last of the season around March 3. Those are the middle dates across the winters of 1991–2020 at Farmers Retreat, IN, 10.9 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 58 days after the last snow.

ZIP 47001 is 10 miles from Milan 5 NE, IN, which stands at 975 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 8 other ZIP codes share the station; its figures are presented in full for 47006 (Batesville). The 2023 USDA Plant Hardiness Zone Map lists ZIP 47001 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.